The invention relates to a superstructure construction comprising a rail disposed above a support layer such as a concrete sleeper and in its turn extending from a securing device such as a ribbed plate,where at least one intermediate layer with a rigidity x is disposed between the support layer and the securing device.
Bedding sleepers on ballast or resorting to designs with a ballastless track and stable, rigid sleeper mountings are known. In the latter case, the sleeper such as a concrete sleeper is placed on asphalt or concrete supporting plates or suitable troughs and then partially cast in place using a sealing compound such as concrete or asphalt.
To achieve a reduction of the structure-borne and airborne sound emitted by a rail in ballastless tracks, a construction is known where a standard rail such as S54 is placed on a cork layer inside a channel comprising concrete or steel parts. In addition, cavities are provided that are filled at the top with a polyurethane/cork mixture to reduce sound.
However, this construction has not brought the desired result, and indeed sound measurements show that there has even been a 10 dB sound increase compared with the ballast construction.
A device for mounting rails for rolling stock is known from DE 89 15 837 U1, in which a ribbed plate is disposed on an elastic intermediate layer whose thickness is at least that of the ribbed plate. The intermediate layer can here have a required elasticity thanks to certain geometrical parameters. The same applies for DE 40 11 013 A1, which relates to a tempered rail structure for high-speed tracks. It is intended here to ensure, by providing a cavity with plastic-modified adhesive mortar, that a direct transmission of heat energy or cooling energy to the rail is prevented.
According to DE 41 38 575 A1, the spring rigidity of an elastic intermediate layer can be designed dependent on the contact force.
EP 0 632 164 A1 contains the proposal to structure the bottom of an elastic intermediate layer such that under load a higher rigidity results, while the transmission of sound is to be restricted at the same time.
An elastic rail support layer with bottom compression points and all-round closed edge strip is known from DE 43 14 578 A1.
A superstructure construction is known from WO 95/06165 in which the rail is supported on a support layer in which a movable section is mounted. The rail is initially supported on this section. If a presettable force is exceeded, the force is passed to the support layer and hence into a support such as a sleeper.
The problem underlying the present invention is to develop a superstructure construction, in particular one on a ballastless track, such that a reduction of structure-borne and airborne sound is achieved.
The problem is substantially solved in accordance with the invention in that the rigidity of the intermediate layer is rated such that at the maximum permissible and/or presettable rail stress in the rail the intermediate layer has substantially non-elastic properties such that further bending of the rail only takes place insubstantially if at all.
In accordance with the invention, the intermediate layer is rated for the permissible or required maximum rail stress, which has the advantage that the rail itself is on a softer support, thus achieving a decoupling between the rail and the sleeper. The effect of this is a lower loading of the support point and in turn a reduction in the structure-borne sound. This can be improved by using as rails those with high moment of inertia and moment of resistance when seen over the rail central axis, for example a filled section rail, so that the rail can perform the function of a support and develop a load-bearing effect. This results in a further decoupling between rail and sleeper, whereby a further reduction is achieved of the structure-borne sound emitted by the rail when it is traversed by rolling stock.
An intermediate layer is proposed that has a low rigidity before the maximum permissible and/or presettable rail stress is reached and a high rigidity when this rail stress is reached.
It is preferably provided here that the intermediate layer has a rigidity x of x.ltoreq.25 kN/mm, preferably 4.ltoreq.x.ltoreq.25 kN/mm, and/or that at the maximum permissible rail stress the intermediate layer has a rigidity x of x.gtoreq.35 kN/mm, in particular x.gtoreq.90 kN/mm, preferably in the vicinity of 100 kN/mm.